Gender Differences in Pain Among Axial Spondyloarthritis Patients

Researchers have discovered that axial spondyloarthritis (axSpA) pain affects male and female patients differently—women with the condition are more likely to experience certain forms of widespread pain. In a new study1 of 170 subjects with presence of axial, peripheral articular, and non-articular pain (108 men, 62 women), axial lumbar pain was most prevalent (in approximately 75% of subjects). It was also more common in women (approximately 84%) than in men (approximately 69%). In addition, nearly 48% of patients experienced pain in the cervical and cervicothoracic spine.

Notably, while axial thoracic pain affected only 32% of subjects, it was approximately three times more common in women when adjusted for variables such as disease duration, age, and weight. Researchers also found that women were two times as likely to experience widespread peripheral articular pain, two and a half times more likely to have cervicothoracic junction pain, and three times more likely to experience widespread axial pain.

Identifying Axial Spondyloarthritis

Medical literature has used the term “axial spondyloarthritis” to describe the “preradiographic” phase of ankylosing spondylitis,2 an inflammatory rheumatic condition that can lead to bone fusion in the spine.3 They suggest that axial spondyloarthritis and ankylosing spondylitis may be two stages of a “single disease entity.”

Axial spondyloarthritis is commonly diagnosed in patients below the age of 45, whose back pain has lasted for more than three months. One of the criteria for an ankylosing spondylitis diagnosis is radiographic evidence of sacroiliitis, or inflammation of the sacroiliac joint.4 Other diagnostic criteria include the presence of one or more features of spondyloarthritis, such as inflammatory back pain, arthritis, psoriasis, Crohn’s disease, or ulcerative colitis.5 Those who carry the human leukocyte antigen HLA-B27, associated with ankylosing spondylitis,6 is another diagnostic marker, when combined with two or more symptoms of spondyloarthritis.

Further Findings

In addition to mapping axial spondyloarthritis pain, the investigators also "relate[d] these findings to key clinical outcomes and the structural properties of the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI)," a commonly used self-reported assessment of disease activity.

“Disease activity outcome [instruments] such as BASDAI are thought of as single constructs, [with] all items in the scale representing disease activity that can be summed to a total score,” which is known as Total Disease Activity, explained study co-author Thijs Swinnen, PT, MT, MSc, PhD candidate at KU Leuven University in Belgium. However, “This [single-factor structure] is not true in women,” he said. Instead, a two-factor structure consisting of Peripheral Disease Activity and Axial Disease Activity may be used.

“This [structure] may cause problems when simply adding up items, and should be explored in future research, especially given the fact that women respond less to anti-inflammatory therapy,” said Swinnen. (Generally, nonsteroidal anti-inflammatory drugs (NSAIDs) are used as a first-line treatment to relieve the pain and stiffness associated with axial spondyloarthritis.)7 “That may be in part explained by the fact that all outcomes were developed when studying mostly male populations,” he added. Swinnen also noted that differences in physiology and disease expression could play a role.

In male subjects, the combination of widespread non-articular peripheral pain (WNAP) and low physician global assessment of disease activity (PGDA) was associated with worse scores on the BASDAI, the Bath Ankylosing Spondylitis Functional Index (BASFI), the Tampa Scale for Kinesiophobia 11-item version (TSK-11), and the Hospital Anxiety and Depression Scale (HADS). In women, the pairing was linked with worse scores on the TSK-11 and the HADS (anxiety) scales. The authors noted that these findings “question current clinical decision-making using disease activity measures in a subgroup of AxSpA.”

Implications for Doctors and Patients

The study results overall are somewhat, but not significantly surprising, according to Elmer G. Pinzon, MD, MPH, DABIPP, medical director, president, and owner of University Spine & Sports Specialists in Knoxville, TN, and PPM editorial advisor. “The topographical analysis of axial spondyloarthritis pain was very helpful, and prevalence of pain was insightful. The gender comparisons were insightful, but possibly attributed to a deficit of female studies to evaluate further,” Dr. Pinzon pointed out. “The clinical correlates and pain spread pattern may be explained by possible autoimmune, arthritic, and medical treatment behavior in females compared to males.”

Dr. Pinzon believes that these findings may have certain implications for doctors, such as the evaluation of topographical analysis patterns in genders, gender symptomology differences, and diagnostic and treatment options to consider with specific emphasis on gender differences. “Given the emphasis of online medical sources which are used by patients, these would be great resources to pursue further medical studies and educational sources on axial spondyloarthritis diagnosis and treatment.”

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